Is the future of content the app? From Android Market to the Windows Phone Marketplace, the iTunes App Store to the Ovi Store, it seems that everyone is app-happy. More than ten billion smartphone and tablet apps have been sold, and App Stores are even coming to the desktop: Apple’s got one already in OS X, and Microsoft will stick its own store in Windows 8.

There’s no doubt that App Stores can provide exposure – we’re quite sure the developers of Angry Birds are particularly grateful – but there are some significant downsides too, especially if you’re in the content creation business. So what are the big concerns about apps? And what are the benefits?

Each platform is different

While the Internet doesn’t quite offer the dream of write-once run-anywhere, it’s pretty close: you can be fairly confident that your customers and/or visitors will be able to access your content, even if they require a plugin to use it – so for example Flash has near-total PC market penetration, while plugins such as Microsoft’s Silverlight are simple and quick to install and aren’t a major obstacle to the typical internet user.

That’s not the case with apps. Some platforms, such as iOS, don’t and will not support Flash; others should support it but don’t, so for example some Android tablets are currently shipping with the promise of Flash support. There are inconsistencies with video, too. Google has announced that its Chrome browser – and presumably its forthcoming app-based Chrome OS – will dump support for H.264 video in favour of WebM video, but while iOS devices can run H.264 they don’t support the VP8 video enclosed in WebM.

The result of all this is that unlike the web, where you can generally code for a common denominator (relatively recent browser, Flash), you need a different collection of technologies for each platform. The AIR app you’ve built for a BlackBerry PlayBook can’t simply be exported in a different file format for use on an iPad. And the problem with that is…

If a platform changes, you’re stuffed

Nokia’s decision to embrace Windows Phone for its future smartphones is great news for Microsoft, of course, but it’s not brilliant news for developers who embraced the Qt development environment, which the move has essentially rendered obsolete. Building for a particular App Store could mean investing in a development environment that you might not be able to use if your chosen Store provider switches allegiance.